From 1524ac986ff38ec691062b82e821f09aa6011524 Mon Sep 17 00:00:00 2001
From: Harihara Kadayam <hkadayam@ebay.com>
Date: Thu, 12 Jan 2023 17:18:05 -0800
Subject: [PATCH] Expand buffer functionality (#389)

---
 include/libnuraft/buffer.hxx | 14 ++++++++++++++
 src/buffer.cxx               | 20 +++++++++++++++++++-
 tests/unit/buffer_test.cxx   | 14 ++++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/include/libnuraft/buffer.hxx b/include/libnuraft/buffer.hxx
index f4885fb6..bda6f483 100644
--- a/include/libnuraft/buffer.hxx
+++ b/include/libnuraft/buffer.hxx
@@ -64,6 +64,20 @@ public:
      */
     static ptr<buffer> clone(const buffer& buf);
 
+    /**
+     * Expand the current buffer to new size (which is expected to
+     * bigger than current size) and return a new buffer. It will copy
+     * the existing buffer.
+     *
+     * WARNING: It will still retain the current position of the passed
+     * buffer and the new ptr buffer (i.e. ret_buf->pos() == buf->pos())
+     *
+     * @param buf Pointer to buffer which will be realloced
+     * @param new_size New size of the buffer
+     * @return Expanded buffer instance
+     */
+    static ptr<buffer> expand(const buffer& buf, uint32_t new_size);
+
     /**
      * Get total size of entire buffer container, including meta section.
      *
diff --git a/src/buffer.cxx b/src/buffer.cxx
index 4d1ff965..f901e5ed 100644
--- a/src/buffer.cxx
+++ b/src/buffer.cxx
@@ -97,7 +97,7 @@ ptr<buffer> buffer::alloc(const size_t size) {
 
     if (size >= 0x80000000) {
         throw std::out_of_range( "size exceed the max size that "
-                                 "cornrestone::buffer could support" );
+                                 "nuraft::buffer could support" );
     }
     num_allocs++;
     num_active++;
@@ -144,6 +144,24 @@ ptr<buffer> buffer::clone(const buffer& buf) {
     return other;
 }
 
+ptr<buffer> buffer::expand(const buffer& buf, uint32_t new_size) {
+     if (new_size >= 0x80000000) {
+        throw std::out_of_range( "size exceed the max size that "
+                                 "nuraft::buffer could support" );
+    }
+
+    if (new_size < buf.size()) {
+        throw std::out_of_range( "realloc() new_size is less than "
+                                 "old size" );
+    }
+    ptr<buffer> other = alloc(new_size);
+    byte* dst = other->data_begin();
+    byte* src = buf.data_begin();
+    ::memcpy(dst, src, buf.size());
+    other->pos(buf.pos());
+    return other;
+}
+
 size_t buffer::container_size() const {
     return (size_t)( __size_of_block(this) +
                      ( ( __is_big_block(this) )
diff --git a/tests/unit/buffer_test.cxx b/tests/unit/buffer_test.cxx
index d7b83aac..0b51b52f 100644
--- a/tests/unit/buffer_test.cxx
+++ b/tests/unit/buffer_test.cxx
@@ -117,6 +117,20 @@ int buffer_basic_test(size_t buf_size) {
     ulong long_val_copy = lbuf1->get_ulong();
     CHK_EQ( long_val, long_val_copy );
 
+    ptr<buffer> buf4(buffer::alloc(sz_int * 100));
+    buf4->pos(0);
+    for (int i = 0; i < 100; ++i) {
+        buf4->put(i);
+    }
+    buf4 = buffer::expand(*buf4, sz_int * 200);
+    for (int i = 0; i < 100; ++i) {
+        buf4->put(i + 100);
+    }
+    buf4->pos(0);
+    for (int i = 0; i < 200; ++i) {
+        int32 val = buf4->get_int();
+        CHK_EQ( i, val );
+    }
     return 0;
 }